Neural systems underlying the influence of sound shape properties of the lexicon on spoken word production: do fMRI findings predict effects of lesions in aphasia?

Previous behavioral work has shown that the phonetic realization of words in spoken word production is influenced by sound shape properties of the lexicon. A recent fMRI study (Peramunage, Blumstein, Myers, Goldrick, & Baese-Berk, 2011) showed that this influence of lexical structure on phonetic implementation recruited a network of areas that included the supramarginal gyrus (SMG) extending into the posterior superior temporal gyrus (pSTG) and the inferior frontal gyrus (IFG). The current study examined whether lesions in these areas result in a concomitant functional deficit. Ten individuals with aphasia and 8 normal controls read words aloud in which half had a voiced stop consonant minimal pair (e.g. tame; dame), and the other half did not (e.g. tooth; (*)dooth). Voice onset time (VOT) analysis of the initial voiceless stop consonant revealed that aphasic participants with lesions including the IFG and/or the SMG behaved as did normals, showing VOT lengthening effects for minimal pair words compared to non-minimal pair words. The failure to show a functional deficit in the production of VOT as a function of the lexical properties of a word with damage in the IFG or SMG suggests that fMRI findings do not always predict effects of lesions on behavioral deficits in aphasia. Nonetheless, the pattern of production errors made by the aphasic participants did reflect properties of the lexicon, supporting the view that the SMG and IFG are part of a lexical network involved in spoken word production.